Gem faceting apparatus

ABSTRACT

A faceting apparatus capable of automatically cutting a predetermined pattern of facets on rough gems. The machine basically includes a gem holder and an angularly adjustable and movable grinding surface. The gem is held at a stationary location while the grinding surface is movable in orientation for cutting a series of pre-selected angular facets. The gem itself might also be angularly indexed and axially located relative to the grinding surface to control depth of cut during a grinding step.

United States Patent I191 Hoffman Mar. 19, 1974 [5 1 GEM FACETING APPARATUS [76] Inventor: Douglas L. Hoffman, W. 3507 La I Crosse, Spokane, Wash. 98126 [22] Filed: Feb. 2, 1972 [2]] Appl. No.: 222,731

[52] US. Cl.... ..51/l 20, 5l/229 [51] Int. Cl B24b 9/16 [58] Field of Search 51/43, 90, 120, 229;

[56] References Cited UNITED STATES PATENTS 2,177,644 10/1939 Finke 51/90 X 1.461.149 7/1923 Hunt 1.240.313 9/1917 Challet 51/120 FOREIGN PATENTS OR APPLICATIONS 448.284 6/1936 Great Britain 125/30 Primary ExaminerHarold D. Whitehead Attorney, Agent, or FirmWells, St. John & Roberts 57] ABSTRACT A faceting apparatus capable of automatically cutting a predetermined pattern of facets on rough gems. The machine basically includes a gem holder and an angularly adjustable and movable grinding surface. The gem is held at a stationary location while the grinding surface is movable in orientation for cutting a series of pre-selected angular facets. The gem itself might also be angularly indexed and axially located relative to the grinding surface to control depth of cut during a grinding step.

17 Claims, 19 Drawing Figures 7 PAIENIEMM 9 I974 SHEET 2 BF 5 FlG 4 PATENTEDIIAR 19 m4 l 77 sum 3 or 5 FIG 5 Pmsmzummn 3.797.177

sum nor 5 FIG 8 A FIG1O FIG 9 PAIENTEDHAR 19 1914 SHEET 5 OF 5 H614 H615 1' H618 H619 l GEM FACETING APPARATUS BACKGROUND OF THE INVENTION Faceting machines in current use usually comprise a grinding wheel fixed to rotate in a selected plane (usually horizontal), and a gem holder or dop arm adjustably positioned above and extending angularly downward to the grinding surface. The dop arm usually provides an adjusting and locking means which allows the operator to pre-select a facet angle. Once the angle has been selected, the operator cuts the facet by angularly urging the stone at the outer end of the dop arm against the grinding wheel until the dop arm engages a stop. This process must be repeated for every cut. Some gem designs require hundreds of separate cuts. With several separate adjustments to be made for each cut, the possibility for human error becomes tremendous. Further,

the value of a cut gem is dependent not only on the quality of the stone itself, but also on uniformity in the facet cuts. Eliminating human error is highly desirable.

The present invention comprises a faceting machine having the potential of being operated by computer, thereby eliminating possibilities of human error.

The present structure holds a gem stationary or moves it axially while an angularly grinding surface cuts each facet. The grinding surface is mounted for compound angular movement relative to the gem, including both horizontal and vertical adjustment capability. An upwardly projecting curved track adjustably supports the grinding surface for the vertical angular adjusting components. The track, in turn, is supported by a 360 horizontally rotatable disc, facilitating compound angular adjustment by adding the horizontal angular adjusting components. i

Since all angular adjustments of the grinder can be motor-controlledit is possible to perform the gem cutting operations in a sequence controlled by a suitably programmed computer.

SUMMARY OF THE INVENTION The described invention relates to a gem faceting apparatus that essentially includes a stationary base and a .dop.munted to the base-for supporting a gem at a fixed location. relative to the base. .Thegemf is aligned along-a first reference axis on the base. Apowered grinding surface is movably supported on the base for angular adjustment in a plane. containing the reference axis. Thejgrinding surface intersects the reference axis during a faceting. operation. Power devices are operatively. connected between the base andthe support means for the grinding surface and are operable to vary the angle of intersection of the grinding surface with respect to the reference. axis through the gem. By repeated retraction of the gemand grinding surface relative to one another and reorientation of these two elements with respect" to each other, one can cut a preselected facet pattern about the gem in a machinecontrolled pattern. 7

It is a first object of this invention to provide an effective apparatus for repetitive faceting of gems in a production operation. This is to be contrasted with normal faceting machines which are substantially under manual control and which require considerable skill on the part of the human operator.

Another object of this invention is to provide a unique faceting apparatus which can be stepped in a pre-selected or programmed sequence by machine or computer controls.

Another object of this'invention is to provide a faceting machine wherein the gem being faceted is held at a pre-selected location and the grinding surface for cutting the facets is moved about the gem in an angular pattern corresponding to the facet configuration desired on the finished gem.

Another object of the invention is to provide an extremely versatile faceting apparatus capable of forming a wide variety of facet patterns on various sized gems without requiring machine modifications or special design of the apparatus.

These and further objects and advantages of the invention will be evident from the following disclosure, taken together with the enclosed drawings, which illustrate a preferred form of the apparatus in schematic detail.

BRIEF DESCRIBT ION OF THE DRAWINGS In the accompanying drawings:

FIG. 1 is a sectioned side elevational view of my invention;

FIG. 2 is a side elevation view taken along line 22 in FIG. 1;

FIG. 3 is a sectioned plan view taken along line 3-3 in FIG. 1;

FIG. 4 is a detailed elevation view of the gem holding apparatus of my invention;

FIG. 5 is a sectional plan view taken along line 5-5 in FIG. 1;

FIG. 6 is a reduced plan view of my machine;

FIG. 7 is a fragmentary side elevation of the object of FIG. 6;

FIG. 8 is an elevation view showing the gem holder of FIG. 4 employing a clamp rotating means;

FIG. 9 is an enlarged plan view of the object of FIG.

FIG. 10 is an elevational view illustrating an alternate form of gem holder;

FIG. 11 is a fragmentary enlarged view of a vacuum operated gem holder;

FIG. .12 ia a diagrammatic representation illustrating the procedure for cutting a Marquise design;

FIG. 13 is a similar diagrammatic illustration showing the procedure for cutting circular designs; and

FIGS. 14-19 illustrate different types of designs capable of being produced by my invention.

' DESCRIPTION OF A PREFERRED EMBODIMENT The general concept of the present apparatus can best be understood from FIGS. 1 and 2. The faceting machine is mounted to a stationary base 10. The gem l3is located at the outer or upper end of a dop 12. The dop l2 and gem 13 are aligned along a first upright axis (X-X), shown in the drawings as being vertical with respect to base 10. The desired facets about the upper portion of gem 13 are cut by a grinding surface 17 illustrated as being the outer plane surface of an abrasive Wheel that is rotatably powered on a shaft 19. During a faceting operation, the grinding surface 17 is movably located relative to the supporting framework on base l0 and with respect to gem 13 so as to grind or polish the gem surface along .the desired planes and to the depths required by the desired finished gem configuration.

The grinding surface 17 of this apparatus is mounted for movement relative to gem 13. By proper control of the location of gem l3 and the orientation and positioning of grinding surface 17, the faceting of a gem can be automated and controlled by electrical or mechanical signal generation. This can be accomplished in the faceting of reproducible artificial gems.

In the preferred structure, the grinding surface 17 is movable about a selected circular or arcuate path in a vertical plane containing the axis XX. This plane extends across FIG. 1 and would be viewed on edge in FIG. 2. There also is provision for rotational indexing of grinding surface '17 and gem 13 relative to one another about axis X-X as a center. In addition, the grinding surface 17 can be angularly indexed about a second axis (YY) independently ofits relation to axis XX. Axis YY is parallel to and spaced from the first axis XX. Finally, axis YY can be moved to vary the radial separation between axis XX and axis YY, permitting variation in the arcuate curvature of the path of surface 17 about a gem centered along axis XX.

Since the gem 13 is typically cut by producing a series of polished plane facets about its exterior surfaces, it is necessary to provide clearance between grinding surface 17 and gem 13 between individual facet operations except in those instances where curved gem surfaces are desired, such as in pre-forming operations. Such clearance can be alternately provided by controlled translational movement of dop 12 along axis XX, or by controlled translational movement of grinding surface 17 along the rotational axis of shaft 19 or by horizontal movement of grinding surface 17.

Such clearance can be achieved by lowering gem 13 from its grinding position. It can also be achieved by retracting grinding surface 17 along the axis of shaft 19 or by moving surface 17 radially outward from the axis XX.

Referring now in detail to the drawings, base supports a fixed upright hollow pedestal 11 centered along the first axis XX. A telescoping dop support 20 is located within pedestal 11 and carries dop 12 at its upper end in such fashion as to raise or lower vertical dop 12 along the first axis XX. Dop 12 protrudes upwardly from an indexing motor 21 at the upper end of dop support 20. The indexing motor 21, when provided as shown, is capable of revolving and angularly positioning dop 12 and gem 13 about the first axis XX.

The operative grinding surface 17 is movably carried by support means extending over gem 13. As illustrated, this support means includes a pair of inwardly facing curved semicircular tracks 22. Tracks 22 movably mount a support unit 23 carrying the motor 24 that rotates shaft 19.

The support means comprising tracks 22 and support unit 23 are adjustably mountedto pedestal 11 by a combination of adjustable support elements that provide the required degree of movement of the grinding surface 17 about the periphery of gem 13. Due to the wide variety of gem configurations, considerable latitude in the choice of a selected path of movement of the grinding surface 17 is necessary in order to provide a versatile machine for faceting operations.

Pedestal l1 rotatably supports a turntable l4 supported by annular bearings 18 which locate turntable 14 on pedestal 11 for rotation about the first axis XX. A horizontal eccentric ring 15 is rotatably mounted to ring 14 for rotation relative to turntable 14 about the second axis YY.

Provision is preferably made for variation of the spacing between the axis YY for ring 15 and the axis XX of turntable l4 and 'gem 13. As will be evident below, this permits change of the curved path of the grinding surface 17 as it is indexed about the gem.-

As can be seen in FIGS. 1 and 2, ring 15 is rotatably supported by annular bearings 34 centered about axis YY. The bearings 34 are interposed between the lower surface of ring 15 and the upper surface of a movable support plate 9 that is part of turntable 14. Plate 9 is movably guided on the main structure of turntable 14 by guides 36 providing dovetail ways which permit horizontal movement of plate 9 in a straight path. Such movement is controlled by a motor 37 on turntable 14 that powers a worm 37a that meshes with a worm gear 37b on plate 9. The translational motion of plate 19 is facilitated by transverse roller bearings 39.

The tracks 22 are shown as being fixed to horizontal annular plates 26 which are guided by guides 27 forming dovetail ways across the upper surface of ring 15 (FIGS. 2 and 5). The plates 26 can be shifted in a plane perpendicular to the axes XX and Y-Y to vary the location of tracks 22 and grinding surface 17 with respect to the second axis YY.

Turntable 14 is rotatably powered by a motor 28 fixed to pedestal 11 (FIGS. 1, 3). The lower portion of turntable 14 provides circular worm gear 30 which meshes with a worm 31 driven by motor 28. Turntable 14, when powered by motor 28, rotates or pivots relative to the stationary pedestal 11 about a circular path centered about the first axis XX.

A second motor 32 is fixedly mounted to turntable 14 at the upper surface of plate 9. When operating, it pivots or rotates ring 15 relative to turntable 14. The driving relationship isestablished through a beveled gear drive generally indicated at 33, 35, and centered about the eccentric second axis YY.

The beveled gear drive 33, 35 may be selectively locked by holding the shaft of motor 32 stationary. This results in rotatably locking ring 15 to turntable 14, whereby ring 15 (and the rotational axis YY) can be selectively indexed about axis XX by operation of motor 28. Motor 32 may, however, be activated independently of motor28 to rotate ring 15 independently or simultaneously during rotation of turntable 14. The object of this flexible motor operation is to provide means for varying the eccentricity of grinding surface 17 relative to the gem 13. The combined rotation of ring 15 and turntable 14 in conjunction with suitable indexing about axis XX facilitates the cutting of a variety of gem designs along curved paths which are circular or non-circular.

Tracks 22 are supported on ring 15 for relative horizontal translational movement along the V-guides 27 (FIGS. 2, 5). The movement of tracks 22 is controlled by a motor 38 that drives a worm 40 meshing with a worm gear 41 that is formed integrally at the underside of plate 26. Motor 38 itself is fixed to ring 15 and can be operated to move tracks 22 simultaneously during rotation of ring 15 if such simultaneous motion is required.

The tracks 22 (FIGS. 5-7) are semi-circular, being illustrated as generated about a center shown at 25 (FIG. 1). They cooperatively carry the support unit 23 by providing opposed inwardly facing arched channels for guide rollers, slides or other track supported elements. As illustrated, one track 22 also includes an integral worm gear 44a which is in meshing engagement with a worm 44 powered by motor 43 (FIG. 1). Selective operation of motor 43 causes the support unit23 to be moved along tracks 22.

A similar motor 45 and worm 46, mounted within the support unit 23, serve to pivot the unit 23 about a worm gear 42 that is slidably mounted by tracks 22. Worm gear 42 does not rotate and acts as a reactive member. Motor 45 controls angular positioning of support unit 23 and grinding surface 17 relative to tracks 22, facilitating compound angular adjustment of grinding surface 17 during a faceting operation.

The grinding surface 17 may be axially movable along the axis of shaft 19 by means of a telescoping as-, sembly 47 interposed between the support unit 23 and motor 24. The retracted or inoperative position of these elements is shown in full lines in FIG.'1, while the extended or operative position is shown in dashed lines. The selective extension of grinding surface 17 may be utilized to axially position the surface to a selected limit during grinding of a facet. After extension tov a preset stop corresponding to a selected facet depth, the grinding surface 17 may be retracted for subsequent indexing of the grinding surface 17, gem 13, or both, in preparation for a subsequent faceting operation.

Further details of an exemplary arrangement for securing and indexing a gem 13 are illustrated in FIGS. 4, 8, 9 andll. The illustrated structure, which may be used in place of more conventional adhesives-or wax,

utilizes an upright suction tube 48 that has a concave conical upper or outer end. The gem 13 is seated at this end upon a resilient pad 49. The pad .49 is constructed ofa resilient material that has hea'tresi stive properties.

Vacuum pressure is selectively applied through tube 48 to draw the gem l3 downwardly against the outer surface of pad 49.. Pad 49, being'resilient, can conform to the shape of the gem 13 and to the end of the tube 48, thereby creating an effective seal during handling of gem13.

Gem 13 is further held mechanically by amovable clamp arm 51. Arm 51 comprises an upright shafthaving an upper horizontal section 52. As seen in FIG. 9, the section 52 isbifur'cated, providing a laterally spread bearing surface that engages the gem 13 across its upper area. Longitudinal tension is applied to clamp arm 51 through action of an air cylinder 52, fixed to a sleeve 54 rotatably mounted to dop 12. A motor 55 'and worm gear 56 are carried on sleeve 54 and mesh with gear teeth 57 formed integrally on dop arm 12. Selected operation of motor 55 therefore serves torotate the sleeve54' relative to both dop 12 and the'dop support to maintain the clamp'assembly 51 at the side of the gem l3 opposite to that at which a particular facet is being ground. Operation of motor 55 is suitably timed with respect to operation of cylinder 52 so asto momentarily release the clamp assembly 51 during ro-:

tation of sleeve 54and thecl'amp 51 carried thereby.

configuration is desired on each gem. Turret 59 includes a support shaft 58 having a rotatable cone 60 mounted to its upper end, the cone axis being at an angle of 45 relative to the shaft axis of shaft 58. Several dops 61 are spaced about cone 60. Each dop 61 is extended at a 45 incline relative to the axis of cone 60. Therefore, by rotating cone 60 on its axis, each dop 61 may be moved to the upright position illustrated in FIG. 10 as being occupied by dop 61a. By utilizing a turret 59 or other equivalent turret structures, several gems may be faceted in sequence to a common facet configuration. The grinding surface 17 need be set only once to cut 5 specific facet in each of the gems mounted to the dops on the turret 59. This particularly lends itself to production repetitive faceting of gems.

The general scheme of the machine illustrated and described herein provides total flexibility in the faceting of a gem by permitting selective rotation of the gem itself, angular positioning and indexing of grinding surface 17 about several different axes and translational movement of both the gem and grinding surface. Where this degree of movement is not necessary; such as in" the cutting of circular designs, certain of the above mechanisms for adjustment of the gem or grinding surface may be omitted. As an example, it might not be necessary to provide for retraction of the grinding surface 17 in instances where the gem is retracted axially along the axis X-X, this movement being utilized to control the depth of cut during a specific faceting operation.

FIG. 13 diagrammatically illustrates the several steps required in the processing of a circular facet pattern, the path of movement being shown at 63. To accomplish this grinding operation, the ring 15 is locked to pedestal 14 by holding motor 32 inoperative. Rings 15 and pedestal 14 are then simultaneously rotated by operation of motor 28 to move the grinding surface 17 in the circular path shown at 64. The motor 28 can angularly step grinding surface 17 about circular path 64 by electrical inpulses directed by a manual operator or from machine controls set from a computer. As an alternative, the circular grinding operation can also be accomplished by selectively moving the dop 12 along axis X--X and rotating dop l2 byoperation of indexing motor 21. Motor 21, like all the other motors described above, may be computer controlled for incremental rorational movementupon-command. Thenecessary clearance between grinding surface 17 and gem 13 during indexing of the gem relative to the grinding surface may beaccomplished by retracting grinding surface 17 or by retracting the dop 12. After the components are repositioned for the next faceting operation, the grinding surface 17 or gem 13 is extended a pre-selected distance corresponding to the desired depth of cut. After completion of eachfacetingoperation, the retraction and indexing steps are repeated until the desired facet angle has been cut about the periphery of the gem.'The support unit 23 is then repositioned along the tracks 22 for a successive row of facets which are then cut about the gem in a repetitive pattern.

FIG. 12 diagrammatically illustrates the general process for forming a Marquise" design, indicated at 65. Ring 15 is first indexed by motor 32,causing the grinding surface 17 to cut successive facets along the arcuate path shown at fA. Theradius of path A is controlled by operation of motor 37. Motor 32 is then locked and motor 28 is activated to rotate both ring 15 and pedestal 14 to the position indicated by phantom lines in FIG. 12. Motor 28 is then locked and motor 32 is stepped to index the grinding surface 17 during the cutting of facets on the path designated at 13. Upon completion of the facet cutting operation, the grinding surface 17 is repositioned along track 22 and the process is repeated until the gem configuration has been completed.

FIGS. 14-19 show basic outlines of conventional gem designs that can be formed by machine control of this apparatus. FIG. 14 illustrates a Marquise shape. FIG. 15 shows a "Seminavette design which would partially involve an operation similar to that described in the forming of a Marquise" cut to form the two arcuate sides, while the flat top surface may be formed by aligning the grinding surface 17 perpendicular to the imaginary line of intersection of the two arcuate sides. FIG. 16 illustrates a pear" design, incorporating portions of both basic operations shown in FIGS. 12, 13. FIG. 17 shows a Lisbon" cut, involving a variation of the Marquise cutting process. FIG. 18 shows an oval cut that may be produced by a combination of the processes described for Marquise" and circular .cuts. An oval shape may also be formed by utilizing motor 38 simultaneously during operation of motor 28 to vary the position of axis Y-Y while maintaining gem 13 stationary. FIG. 19 illustrates a pear-shaped design incorporating a part of the Marquise design procedure and a repetition of half-circular cuts to form the upper portion.

It is to'be noted that the examples described above are only a selected few of the gem designs that may be produced by this machine. By proper control of the various motors, one may reposition the grinding surface l7 relative to the gem to form any desired pattern of facets about the gem surfaces. The control of these motors can be accomplished by conventional tape controls, using magnetic or punched tape machine controls known in other machining industries. The computer controls can be either special purpose, including mechanical control, or can be supplied by a properly programmed general purpose computer. Many gem designs incorporating geometric configurations of all shapes can be carried out in a production manner by the automatic apparatus generally described above.

Many modifications can obviously be made with respect to the schematic presentation of the physical components of this apparatus. The above description and accompanying drawings are not intended to limit or restrict the scope of this application beyond the definition of the appended claims.

Having thus described my invention, I claim:

1. In a gem faceting apparatus:

a stationary base; 7

a dop mounted to said base along a first axis, the

outer end of said dop including gem mounting means for holding a gem along said first axis; powered grinding surface means;

curved support means movably mounted to said base for movement relative to said base about said first axis and extending across the dop and spaced outwardly therefrom, said support means presenting a concave configuration facing towards said gem mounting means;

said grinding surface means being movably mounted to said curved support means for motion along a path conforming to the concave configuration thereof for permitting angular adjustment of said powered grinding surface means in a plane containing said first axis; first power means operatively connected between said base and said support means for selectively moving said grinding surface means in said plane along said curved support means so as to vary the angular orientation of said grinding surface means with respect to the first axis; and means operatively connected between said curved support means and said base for imparting rotational motion to said curved support means about said first axis. 2. An apparatus as set out in claim 1 further comprising:

means operatively connected between said base and said dop for imparting rotational motion to said dop about said first axis. 3. The apparatus set out in claim 1 further comprising:

means operatively connected between the base and said curved support means mounting said curved support means relative to said base about a second axis that is parallel to and spaced from said first axis. 4. The apparatus set out in 1 further comprising: means operatively connected between the base and said curved support means mounting said curved support means relative to said base about a second axis that is parallel to and spaced from said first axis; and means operatively'connected between the baseand said curved support means for translationally moving the curved support means relative to the base along a plane that is perpendicular to said first axis.

5. The apparatus set out in claim 1 further comprising: I

means operatively connected between the base and said curved support means mounting said curved support means relative to said base about a second axis that is parallel to and spaced from said first axis; and

means operatively connected between the base and said curved support means for translationally moving said second axis relative to the base while maintaining the second axis parallel to said first axis.

6. The apparatus set out in claim 1 further comprising: I

first and second bearing means operatively interposed between the curved support means and said base, said first bearing means being centered about said first axis and said second bearing means being centered about a second axis parallel to and spaced from said first axis.

7. In a gem faceting apparatus:

a stationary base;

a dop mounted to said base along a first axis, the outer end of said dop including gem mounting means for holding a gem along said first axis;

.a first support member rotatably mounted to said base for movement about said first axis;

first power means operatively connected between said first member and said base for selectively moving said first member relative to said base about said first axis;

a second support member mounted to said first member for motion relative thereto;

second power meansoperatively connected between said second member and said first member for selectively moving said second member relative to said first member;

arched track means mounted to said second member extending across said second member and presenting a concave configuration facing toward the gem mounting means of said dop;

and powered grinding surface means movably mounted to said track means for motion along a path conforming to said concave configuration for surface engagement with a gem held by said gem mounting means.

8. The apparatus as set out in claim 7, wherein said second member is mounted to said first member about second axis of rotation parallel to and spaced from said first axis.

9. The apparatus as set out in claim 7, wherein the concave configuration of said track means is centered along a second axis parallel to and spaced from said first axis;

and third support means mounting said second member to said first member for translational movement of said second member relative'to said first member in a direction perpendicular to said first axis.

10. The apparatus as set outin claim 9 wherein said second member is mounted to said first member about an axis of rotation parallel to and spaced from said first axis. i

11 An apparatus as set out in claim 7, further comprising: v I

movable dop support means mounting said dop to said base for selectively translating said dopalong .said first axis.

12. An apparatus as set out in claim 11, wherein said dop support means mounts said dop for rotation about said first axis and includes means for angularly indexing the dop about said first axis.

13. In a gem faceting apparatus:

a stationary base;

a dop mounted to said base along-a first axis, the

outer end of the dop including a gem mounting device seating a gem along said first axis in a position releasably fixed to said dop;

a first annular member rotatably mounted to said base about said first axis;

a second annular member rotatably mounted to said first annular member about a second axis parallel to and spaced from said first axis;

a powered grinding surface;

a support for said grinding surface, said support being mounted to said second annular member for rotation about said second axis in unison with said second annular member; said support comprising relatively movable elements adjustably locating the angular relation of the powered grinding surface with respect to said first axis;

and powered means connected to said first and second annular members and to said base for selectively indexing said annular members about said first and second axes.

14. The apparatus as set out in claim 13, further comprising:

a translational support connected between said first and second annular members permitting motion of said second member relative to said first member along a plane perpendicular to said first axis;

and a controllable power device operatively connected between said first and second members for imparting translational motion to said second member relative to said first axis.

15. The apparatus'as set out in claim 13 further comprising:

movable dop support means mounting said dop to said base for selectively translating said dop along said first axis.

16. An apparatus as set out in claim 15, wherein said dop support means mounts said dop for rotation about said first axis and includes means for angularly indexing the dop about said first axis.

17. An apparatus as set out in claim 1 further comprising:

means operatively connected between said base and said dop for imparting translational movement to said dop along said first axis. 

1. In a gem faceting apparatus: a stationary base; a dop mounted to said base along a first axis, the outer end of said dop including gem mounting means for holding a gem along said First axis; powered grinding surface means; curved support means movably mounted to said base for movement relative to said base about said first axis and extending across the dop and spaced outwardly therefrom, said support means presenting a concave configuration facing towards said gem mounting means; said grinding surface means being movably mounted to said curved support means for motion along a path conforming to the concave configuration thereof for permitting angular adjustment of said powered grinding surface means in a plane containing said first axis; first power means operatively connected between said base and said support means for selectively moving said grinding surface means in said plane along said curved support means so as to vary the angular orientation of said grinding surface means with respect to the first axis; and means operatively connected between said curved support means and said base for imparting rotational motion to said curved support means about said first axis.
 2. An apparatus as set out in claim 1 further comprising: means operatively connected between said base and said dop for imparting rotational motion to said dop about said first axis.
 3. The apparatus set out in claim 1 further comprising: means operatively connected between the base and said curved support means mounting said curved support means relative to said base about a second axis that is parallel to and spaced from said first axis.
 4. The apparatus set out in 1 further comprising: means operatively connected between the base and said curved support means mounting said curved support means relative to said base about a second axis that is parallel to and spaced from said first axis; and means operatively connected between the base and said curved support means for translationally moving the curved support means relative to the base along a plane that is perpendicular to said first axis.
 5. The apparatus set out in claim 1 further comprising: means operatively connected between the base and said curved support means mounting said curved support means relative to said base about a second axis that is parallel to and spaced from said first axis; and means operatively connected between the base and said curved support means for translationally moving said second axis relative to the base while maintaining the second axis parallel to said first axis.
 6. The apparatus set out in claim 1 further comprising: first and second bearing means operatively interposed between the curved support means and said base, said first bearing means being centered about said first axis and said second bearing means being centered about a second axis parallel to and spaced from said first axis.
 7. In a gem faceting apparatus: a stationary base; a dop mounted to said base along a first axis, the outer end of said dop including gem mounting means for holding a gem along said first axis; a first support member rotatably mounted to said base for movement about said first axis; first power means operatively connected between said first member and said base for selectively moving said first member relative to said base about said first axis; a second support member mounted to said first member for motion relative thereto; second power means operatively connected between said second member and said first member for selectively moving said second member relative to said first member; arched track means mounted to said second member extending across said second member and presenting a concave configuration facing toward the gem mounting means of said dop; and powered grinding surface means movably mounted to said track means for motion along a path conforming to said concave configuration for surface engagement with a gem held by said gem mounting means.
 8. The apparatus as set out in claim 7, wherein said second member is mounted to said first member about second axis of rotation parallel to and spaced from said first axis.
 9. The apparatus as set out in claim 7, wherein the concave configuration of said track means is centered along a second axis parallel to and spaced from said first axis; and third support means mounting said second member to said first member for translational movement of said second member relative to said first member in a direction perpendicular to said first axis.
 10. The apparatus as set out in claim 9 wherein said second member is mounted to said first member about an axis of rotation parallel to and spaced from said first axis.
 11. An apparatus as set out in claim 7, further comprising: movable dop support means mounting said dop to said base for selectively translating said dop along said first axis.
 12. An apparatus as set out in claim 11, wherein said dop support means mounts said dop for rotation about said first axis and includes means for angularly indexing the dop about said first axis.
 13. In a gem faceting apparatus: a stationary base; a dop mounted to said base along a first axis, the outer end of the dop including a gem mounting device seating a gem along said first axis in a position releasably fixed to said dop; a first annular member rotatably mounted to said base about said first axis; a second annular member rotatably mounted to said first annular member about a second axis parallel to and spaced from said first axis; a powered grinding surface; a support for said grinding surface, said support being mounted to said second annular member for rotation about said second axis in unison with said second annular member; said support comprising relatively movable elements adjustably locating the angular relation of the powered grinding surface with respect to said first axis; and powered means connected to said first and second annular members and to said base for selectively indexing said annular members about said first and second axes.
 14. The apparatus as set out in claim 13, further comprising: a translational support connected between said first and second annular members permitting motion of said second member relative to said first member along a plane perpendicular to said first axis; and a controllable power device operatively connected between said first and second members for imparting translational motion to said second member relative to said first axis.
 15. The apparatus as set out in claim 13 further comprising: movable dop support means mounting said dop to said base for selectively translating said dop along said first axis.
 16. An apparatus as set out in claim 15, wherein said dop support means mounts said dop for rotation about said first axis and includes means for angularly indexing the dop about said first axis.
 17. An apparatus as set out in claim 1 further comprising: means operatively connected between said base and said dop for imparting translational movement to said dop along said first axis. 